Factors and forces involved in the initial events of bacterial adhesion as monitored by atomic force microscopy

Bacteria found in natural aquatic environments have a tendency to adhere to and proliferate on both biological and non-biological surfaces (Costerton et al., 1987; Ofek and Doyle, 1994). Bacteria adhering to surfaces often secrete an exopolysaccharide matrix to produce robust microbial communities known as biofilms that are recalcitrant to any antimicrobial treatment (Costerton et al., 1987; Costerton et al., 1994; Gristina, 1987). Consequently, bacterial adhesion and subsequent biofilm formation onto non-biological surfaces is a critical issue in processes ranging from the biofouling of industrial equipment to dental decay to infections of implanted medical devices. The first and most important step in the establishment of biofilm communities is bacterial adhesion. Bacterial adhesion consists of two kinetically distinct events: the initial, non-specific, reversible interaction of bacteria with a surface followed by the establishment of specific, irreversible, short-range interactions the latter of which involve receptor/ligand binding events (Christensen et al., 1995; Costerton et al. , 1995; Gristina, 1987; Ofek and Doyle, 1994). This research focuses on the initial, nonspecific, reversible forces of interaction between bacteria and inanimate surfaces as bacteria initially approach a solid-liquid interface. An in-depth understanding of the initial events of bacterial adhesion will facilitate the manipulation and control this natural phenomenon.; Research investigating the forces and factors involved in bacterial adhesion commanded the development of a new experimental methodology to directly measure the forces of interaction between bacteria and substrates. This dissertation describes the novel application of the atomic force microscope to investigate the physiochemical forces and biological factors involved in the initial events of bacterial adhesion. The AFM-based bacterial adhesion assay was successful in determining the contribution of the polysaccharide, molecules, lipopolysaccharide and colanic acid, expressed on the E. coli cell surface to bacterial adhesion.